Magnetostatic relay



Dec. 5, 1961 E. ALIZON MAGNETOSTATIC RELAY 2 Sheets-Sheet 1 Filed Dec. 1, 1958 @UHWF [All/MK Fr/ENA/E AL/zou ffakuzrs United States Patent 3,012,152 MAGNETOSTATIC RELAY Etienne Alizon, Strasbourg, France, assignor to Compagnie Industrielle des Telephones, Paris, France, a

corporation of France Filed Dec. 1, 1958, Ser. No. 777,373 Claims priority, application France Dec. 21, 1957 5 Claims. (Cl. 307-88) The present invention concerns control and storage devices magnetostatic relays which can be used more especially in automatic telephony and in remote control.

A magnetostatic relay comprises the elements of a magnetic amplifier, particularly one or more control windings which can be fed with a direct current known as control current, and an output circuit, which depending on the control currents in the control winds, is or is not supplied with direct current referred to as output current.

There is already known from US. patent application Serial No. 693,180, filed October' 29, 1957 now Patent No. 2,946,896 issued July 26, 1960, a magnetostatic relay comprising a transistor connected to the output of a magnetic amplifier and permitting of obtaining a direct output current capable of assuming two clearly determined values as a function of the control ampere-turns.

However, the presence of a filtering condenser in parallel with the utilisation impedance gives the whole an appreciable time constant, the pulling-up and release times of the relay being from to 20 times greater than the period of the reference alternating current.

The present invention relates to a magnetostatic relay in which the presence of the said filtering condenser is no longer necessary for obtaining a direct output current. The response time of the relay then becomes of the order of a half-cycle of the alternating reference current.

Among the objects of the present invention are to obtain an improved bistable relay capable of supplying, dependent upon the energization of the control windings, either a null current or a direct current of substantially constant intensity, as well as a relay that is very fast acting.

The magnetostatic relay according to the invention includes a magnetic amplifier comprising two saturable magnetic cores on each of which there may be wound an operating winding and control, bias and feedback windings, and two circuit portions each comprising one of the operating windings and a rectifier, these two circuit portions being connected in parallel to a transistor and fed with square pulse trains staggered in relation to one another by a half-cycle, i.e., the pulse trains are 180 out of phase.

The transistor whose emitter receives the sum of the two output currents of the magnetic amplifier then operates substantially with direct current, so that it is possible effectively to eliminate the filtering condenser of the aforementioned application.

Further features and advantages of the invention will become apparent in the course of the description thereof which is hereinafter given with reference to the figures of the accompanying drawings, which show by way of example one possible constructional form of a relay according to the invention.

FIGURE 1 is the circuit diagram of the relay.

FIGURES 2 to 7 are curves relating to the operation of the device according to FIGURE 1.

The relay illustrated in FIGURE 1 comprises two saturable magnetic cores a and b, on which a plurality of windings are wound.

A winding 10 or 1b connected in series with a rectifier Rda or Rdb is fed from a source Ea or Eb of alternating current. These two corresponding sources Ba and 3,012,152 Patented Dec. 5, 1961 ice Eb give square pulse trains, one of which is out of phase by a half-cycle with respect to the other. The control windings 2a and 2b are connected in series. The same is the case with the feedback windings 3a and 3b and with the bias windings 4a and 4b. Throughout the following description the algebraic sum of the ampere turns of the windings 2a, 3a and 4a will be the control ampere turns NcIc of the respective saturable core a and likewise the algebraic sum of the ampere turns of the windings 2b, 3b and 4b will be the control ampere turns NcIc for the core b, the sum of the ampere turns for cores a and b constituting the total ampere turns NcIc for the relay.

The relay also comprises between the point C common to the two rectifiers (Rd )a and (Rd)b and the point D, which is connected to the earthed-terminal of the sources Ba and Eb, a chopping circuit including a resistance r connected in series with a constant E.M.F. source having a voltage U0. The resistance r is connected to the negative pole of this direct current source.

Connected to the same point C is the emitter of a transistor T of the p-n-p-junction type, whose base is connected to the point D through an electromotive bias source having a direct current potential U2.

The collector of the transistor is connected to a load impedance R, the other end of which is connected to the negative pole of a source having a direct current potential U1. The positive terminals of the sources of direct current potentials U0, U1 and U2 are connected at D to the earthed terminal of the sources Ea and Eb.

The terminals M, N, P, Q permit of introducing the feedback windings 3a and 3b into the output circuit of the relay when desired. It will be assumed in the following description that these windings are unconnected, that is to say, that the connection NQ has been established.

FIGURE 2 shows the curve of the mean output current Im as a function of the control ampere-turns NcIc supplied by the windings 2 and 4 of one of the magnetic cores. This current Im flows through the winding 1 and the rectifier Rd of one of the magnetic cores.

The curves 1 and 2 of FIGURE 3 represent as a function of time the output currents (Im)a and (Im-)b in the respective windings 1a and 1b for a given value of the control ampere-turns. The curve 3 of the same figure represents the sum (Im)t of these two currents present at the point C of FIGURE 1.

The transistor T will be conductive if the voltage of this point C, that is, that of the emitter, is higher than that of the base. I being the current across the resistance r, the transistor will therefore be conductive i-f:

therefore appears as a threshold current. The curve of FIGURE 4 represents on the one hand the curve of FIG- URE 2 and on the other hand the line I=I0. This line intersects the curve at two abscissa points (NcIc)S and (NcIc)T.

The curve of the current at the input of the emitter as a function of the ampere-turns NcIc is that shown in FIGURE 5.

The current in the collector substantially follows th variations of current in the emitter as long as the voltage of the collector remains lower than that of the base. Beyond this limit, the current is stabilised exactly at a vali: I1 such that the base and collector voltages are equ This value is therefore such that The curve of FIGURE 6 represents the current Is across the load resistance R.

The curve of FIGURE 7 represents the same current Is as a function of the time for a constant value of NcIc higher than S1 (FIG. 5). The pulsations which could appear due to the spacing of the pulses of curve 3 in FIGURE 3 disappear completely in FIGURE-7 by reason of the storage time of the transistor. The transistor therefore operates substantially with direct current and with substantially zero base-collector voltage, which is favourable to its output.

As is mentioned above and as is known in the aforementioned application, the feedback windings may be connected in series between the terminals N and Q instead of having a direct connection therebetween. The feedback windings supplement the action of the control windings 2a and 2b and produce a faster change in the output current when the control ampere turns change the state of the relay. As is more completely described in the aforementioned application, by using feedback windings the output current curve can be modified so that the output current will move from zero to II with a very small change in control ampere turns. Moreover, in using the feedback windings, the output current curve isnot reversible, i.e., the value of the output current is different for the same value of control ampere turns, depending upon whether the output current is zero and the control ampere turns are increasing or the output current has reached the stable value I1 and the control ampere turns are decreasing.

Iclaim:

1. A magnetostatic relay comprising a magnetic amplifier in association with a transistor having an emitter for controlling conduction through the transistor, said magnetic amplifier comprising two saturable magnetic cores on each of which are wound an operating winding and at least one control winding, said amplifier having a pair of output terminals, one of which is connected to said emitter, and two circuit portions each comprising in series a source of square alternating-current pulsw, one of the operating windings and a rectifier, said circuit portions being connected in parallel to said one terminal at the emitter of the transistor, the alternating-current sources supplying in the operating windings of the two saturable magnetic cores two pulse trains out of phase by a half-cycle in relation to one another, so that the transistor is fed with a substantially direct current.

2. A magnetostatic relay according to claim 1, characterised in that a chopping circuit is connected to the output terminals of the magnetic amplifier to control the potential difference between these output terminals, said transistor having a collector and a base with a load impedance connected to ,the collector of the transistor, a

first constant voltage source being disposed in the chopping circuit, a second constant voltage source being connected in the base circuit of the transistor and a third constant voltage source being disposed in series with the load impedance of the relay, the three poles of like sign of the said three constant voltage sources being connected together and to the other terminal of the amplifier, which other terminal is common to the two alternating current sources.

3. A magnetostatic relay according to claim 2, wherein there are included in the circuit of the collector of the transistor two feedback windings supported respectively by the saturable magnetic cores of the magnetic ampli- 4. A magnetostatic relay according to claim 3, wherein said control windings of the respective cores are connected in series and wherein the feedback windings of the respective cores are connected in series with the collector circuit to achieve the same value of output current in the respective operating windings when the latter are conductive.

5. A magnetostatic relay comprising a magnetic amplifier having a pair of saturable magnetic cores, each said core having an operating winding and a rectifier connected in series therewith, potential sources for energizing each said operating winding with square pulses, said potential sources being coordinated to supply said pulses to the respective windings out of phase with respect to each other, said operating windings being connected to a terminal constituting one output terminal of the magnetic amplifier, said sources of square pulses being interconnected at a second terminal, a transistor including a control electrode for controlling its conduction, said transistor being connected between said terminals with said control electrode connected to one of said terminals, said transistor having an output circuit with a load connected therein, said magnetic cores each having at least one control winding thereon for controlling the current in said operating windings, said control windings providing for a predetermined number of ampereturns therein substantially the same value of current through each of said operating windings when the latter are conductive and said pulses having a predetermined relationship with respect to each other and to the storage time of the transistor so that the transistor is controlled by a substantially direct current and so that said load is traversed by a current that is either null or of a predetermined stable value depending upon the control ampere-turns in said control windings.

References Cited in the file of this patent UNITED STATES PATENTS 2,894,180 Price July 7, 1959 2,915,645 Monin Dec. 1, 1959 2,946,896 Alizon July 26, 1960 

